Connection of a wind energy plant rotor blade to a rotor hub

ABSTRACT

The invention relates to a rotor blade in a wind energy plant, comprising at least one recess arranged in the area of the base ( 6 ) of the rotor blade and extending substantially perpendicular to the longitudinal axis of said rotor blade ( 6 ) to accommodate a cross-bolt ( 16,18 ) which can be joined to a traction element ( 20,22 ) to enable connection of the rotor blade ( 6 ) to a rotor hub ( 11 ) in a wind energy plant ( 1 ). The invention further relates to a rotor for a wind energy plant, comprising a rotor hub ( 11 ) and at least one rotor blade ( 6 ) secured to said hub ( 11 ), in addition to a wind energy plant. The invention is characterized in that the recess only partially crosses through the rotor blade.

The present invention concerns a rotor blade for a wind energy plant,with at least one recess, arranged in the region of the rotor blade baseand extending essentially transversely to the longitudinal access of therotor blade, for accommodating a cross bolt, which can be coupled to atensioning element for the connection of the rotor blade to a rotor hubof a wind energy plant.

The invention further concerns a rotor for a wind energy plant with arotor hub and at least one rotor blade fastened to the rotor hub, aswell as a wind energy plant with such a rotor.

A rotor blade as well as such a rotor for a wind energy plant, of thetype named in the introduction, are known. They find application, forexample, in a wind energy plant with the designation AEOLUS II, whichwas developed as an experimental plant by Messerschmidt-Bölkow-Blonm(MBB) (“Windkraftanlagen”, Erich Hau, 2^(nd) ed., Springer-Verlag,Berlin, Heidelberg, New York, ISBN 3-540-5743-1, p. 203).

With wind energy plants, the fastening of the rotor blades, which aresubjected to considerable forces, to the shaft of the wind energy plant,which is coupled to the generator, is a general problem, since due tothe forces acting upon the rotor the components used are exposed toextreme stresses. The structural form of the so-called rotor bladeconnection is thus of great significance.

With one known wind energy plant, the rotor blade, consisting of acompound material, is connected in the region of the so-called rotorblade base, i.e. in the rotor blade's end region that is to be coupledto the rotor hub, to a metallic flange that consists of an inner andouter ring flange; in this, the rotor blade base is set between theinner and the outer ring flange and is fastened by means of an adhesiveand a threaded connection. For the producing of the threaded connection,a bolt is inserted through a passage bore, which passes completelythrough the rotor blade, into the rotor blade and screwed. The flange isscrewed to the rotor hub at its end opposite to the rotor blade base.This construction of the rotor blade connection is relativelycomplicated and heavy structurally, since the metallic flange has a highweight. Especially disadvantageous is the fact that the rotor blade issignificantly weakened in the region of the rotor blade base by thepassage bore for receiving the bolt.

An additional, known wind energy plant displays as the rotor bladeconnection a steel flange joint, in which the rotor blade base isclamped between an inner and an outer flange and the two flanges arescrewed together. The joining of the two flanges with the rotor hubtakes place by means of a spaced-apart flange ring, with the aid ofhigh-strength expansion screws. In this construction the metallicflanges contribute very often up to a third to the total weight of therotor blade. Furthermore, the force progression is unfavorable, due to aradial offset between the rotor blade base and the spaced-apart flange,since this leads to an undesired lever effect.

In the case of the above mentioned experimental AEOLUS II, a so-calledcross-bolt connection is used, in which the so-called cross bolts arearranged in passage bores in the region of the rotor blade base (i.e.the hub-side end region of the rotor blade), which passage bores areformed in the rotor blade and pass completely through the latter. Thecross bolts arranged inside the passage bores are laminated into therotor blade and serve as anchoring elements inside the rotor blade. Thecross bolts are in each case connected to a tensioning element, formedas a bolt-shaped tension rod, that is screwed together with the rotorhub. By means of the tensioning element, which is subjected to tension,the rotor blade is pressed against the hub and thus held. In thisconstruction it is likewise especially disadvantageous that the rotorblade is greatly weakened in the region of the rotor blade base by thepassage bores for receiving the cross bolts. Furthermore, the forceprogression in the region of the flange-like rotor hub is unfavorable.

The task of the present invention consists in specifying a rotor, arotor blade, and a wind energy plant, in which the disadvantages of theprior art are to a large extent avoided, and which have an easilyproducible and secure connection between the rotor blade and the rotorhub, which connection is able to withstand extreme stresses.

According to the invention, this task is accomplished in a rotor bladeas well as a rotor of the type named in the introduction by the factthat the recess passes only partially through the rotor blade.

By means of the design, in accordance with the invention, of a recessthat passes not completely, but rather only partially, through the rotorblade, the rotor blade is weakened in the region of the rotor blade baseto a substantially lesser degree than is the case with the prior art, inwhich provision is made for a passage bore that passes completelythrough the rotor blade for receiving the cross bolt. Achieved accordingto the invention is the fact that the rotor blade, by virtue of thereduced material weakening, can withstand greater stresses withcomparable structural size. A rotor blade is thus more securely fastenedto a hub of a wind energy plant, and the structural size of the rotorblade connection can be kept relatively small, so that it can be builtso as to be comparatively light. The rotor blade connection according tothe invention withstands in a lasting manner the extreme stresses towhich the rotor blade and the rotor hub are subjected in the region ofthe rotor blade base.

With the use in particular of fiber-reinforced epoxy-resin compoundmaterial as a lighter and at the same time more robust material forrotor blades, a durable anchoring of the cross bolts in the rotor bladebase can be realized. In this case there results a favorableintroduction of force from a cross bolt to the epoxy-resin compoundmaterial of the rotor blade.

An especially preferred implementation of the rotor blade according tothe invention and of the rotor blade is characterized by the fact thatthe recess is formed as a pocket hole. In this way, the recess can beformed in the rotor blade in a particular simple manner from theoutside. A further advantage results from the fact that the cross bolts,which in the assembled state are arranged inside the pocket holesaccessible from the outside, can, if need be, be replaced without anydamage to the rotor blade being necessary.

Provision can advantageously be made in the rotor blade for severalspaced-apart pocket holes for receiving several cross bolts, sincethereby the strength of the rotor blade connection can be substantiallyincreased, which is necessary in particular in the case of very largewind energy plants. The pocket holes can be spaced in such a manner thatthe material is only insignificantly weakened by the pocket holes.

Especially preferable is an implementation of the invention in which therotor blade has an enlarged cross section in the region of the rotorblade base and the pocket holes or holes is/are arranged in the regionof the enlarged cross section. Also, through this measure the loadcapacity of the connection between rotor blade and rotor hub can besignificantly increased, since the rotor blade, due to the enlargementof the cross section in the region of the rotor base, is subjected tosubstantially smaller stresses and can therefore be impinged upon bygreater forces. By means of the arrangement, according to the invention,of the pocket holes in the region of the enlarged cross section, afavorable introduction of force from the cross bolts to the material ofthe rotor blade is possible, while a substantially lesser surfacepressure occurs at the contact surface between the cross bolts and theinner surface of the recess.

According to an especially preferred implementation form of theinvention, the cross section of the rotor blade is enlarged on bothsides in the direction of a hub-side end section of the rotor blade. Inthis way a symmetrical introduction of force from the cross bolts intothe robust rotor blade is realized. According to a further developmentof this implementation example, the rotor blade displays twoopposite-lying thickening sections, in each case formed as one piecewith the rotor blade, and the pocket holes are arranged at leastpartially in the region of a thickening section. The thickeningsections, which contribute to the cross section enlargement, can beformed in a simple manner through the laminating on of several layers offiber laminate material and epoxy resin.

Especially preferred, furthermore, is an implementation form in whichthe rotor blade displays in the region of the rotor blade base anessentially pipe-shaped end section, in which several pocket holes areformed on the inside and outside. A pipe-shaped end section can beattached to the rotor hub in an especially uniform and simple manner andis of particular advantage in the case of very large wind energy plants,in which extreme forces appear, the rotor blades of which transitionfrom the pipe-shaped end section for attachment into a wing-profilesection.

A further development is characterized through several bores, eachjoined with a pocket hole and extending essentially in the direction ofthe longitudinal axis of the rotor blade, for receiving in each case atensioning element that can be connected to a cross bolt. In this mannerthe tensioning elements are advantageously arranged partially inside therotor blade in the bores and can at the same time engage a bore that isarranged centrally in the cross bolts and provided with a tread, so thatthe cross bolts are impinged upon by the tensile force in a symmetricalmanner and are arranged inside the rotor blades essentially free ofmoments.

A favorable introduction of force and a high strength result when thepocket hole or holes is/are essentially cylindrical and display a depththat is approximately equal to a third of the cross section of the rotorblade in the region of the rotor blade base.

A great lightness of material combined with a high degree of strengthresults from an implementation form in which the rotor blade consistsmainly of a glass-fiber-reinforced epoxy-resin compound material.

The previously explained advantages of a rotor blade according to theinvention result in a similar way from a rotor for a wind energy plantof the type mentioned in the introduction, which plant is equipped witha rotor blade according to the invention. In order to avoid repetition,therefore, with respect to these advantageous effects reference is madeto the foregoing exposition.

A preferred further development of the rotor according to the inventionis distinguished by the fact that the rotor hub displays a rotary, incross section essentially T-shaped flange section for the connecting ofthe rotor blade and that the rotor blade is screwed to the flangesection by means of several tensioning elements, which are connected ineach case to a cross bolt anchored on the rotor blade. Through theadvantageous symmetrical T-shaped flange section a symmetrical forceintroduction from a rotor blade to the hub can be realized, since formedin the two open sections of the T-shaped flange section, lyingessentially in one plane, are the passage bores through which thetensioning elements project. Advantageously, the several tensioningelements are arranged parallel to each other in pairs and essentially intwo rows that are concentric with each other. In this, the tensioningelements lying opposite each other in pairs can lie directly opposite orstaggered with respect to the tensioning elements of the other row.

The advantages according to the invention are also realized by a windenergy plant that is equipped with a rotor and/or a rotor blade of theabove-described type; with respect to the advantages according to theinvention that are attainable thereby, reference is made to theforegoing explanations in connection with a rotor blade and rotoraccording to the invention.

The invention is described in the following in the context of animplementation example of a rotor of a wind energy plant, with referenceto the accompanying drawings. They show:

FIG. 1: a schematic representation of a wind energy plant according tothe invention

FIG. 2: a sectional representation of the attachment, according to theinvention, of a rotor blade to a rotor hub of a wind energy plant (rotorblade connection)

FIG. 3: a schematic view of an end section of the rotor blade, accordingto the invention, from FIG. 1

FIG. 4: a further schematic view of an end section of an alternativeimplementation example of a rotor blade according to the invention

The wind energy plant 1 represented in FIG. 1 comprises in essence atower 3 and a pod 5 attached to the latter for accommodating a generator7 as well as a rotor 9 connected directly to the generator. The rotor 9displays a rotor hub 11 as well as, for example, three rotor blades 2fastened to the rotor hub 11. Through the wind force acting upon therotor blade 2, the rotor hub 11 is rotated in order to drive thegenerator 7.

The generator 7, formed as a ring generator, displays a stator 13 and arotor 15. The rotor 15, together with the rotor hub 11, is supported onsupport pin 19 by means of main supports 17, which support pin is firmlyconnected to a machine carrier 21. The machine carrier 21 is mounted onthe tower 3 so as to be swingable by means of an azimuth motor 23. Alsoattached to the machine carrier 21 is a wind gauge 27.

FIG. 2 shows in a sectional representation a section of a rotor blade 2of a wind energy plant 1, which, for example, can be a matter of aso-called horizontal-axis wind energy plant.

The rotor blade 2 represented in partial view in FIG. 2 is produced in astructurally light manner from a fiber-reinforced epoxy-resin compoundmaterial and is firmly connected to the rotor hub 11 by means of a rotorblade connection 29 (FIG. 1) in accordance with the invention, the rotorblade 2 being firmly screwed to a rotary flange section 4, essentiallyT-shaped in cross section, which in turn is rigidly joined to the rotorhub 11. The section of the rotor blade 2 represented in FIG. 1 is—justas the flange section 4—formed in an essentially rotary and pipe-shapedmanner, and transitions, with increasing distance from the rotor hub 11,into the wing profile, which is not represented. Arranged between therotor blade connection 29 and the rotor hub 11 is a blade adapter 31.With the aid of a blade adjustment motor, a rotor blade 2, together witha blade connection 29 and a blade adapter 31, can be rotated around alongitudinal axis of the rotor blade 2.

FIG. 2 illustrates the two-sided enlargement, according to theinvention, of the cross section or thickening of the rotor blade 2 inthe region of the rotor blade base 6, i.e. in the implementation examplethe end region of the essentially pipe-shaped section of the rotor blade2, which in the assembled state is connected to the flange section 4 ofthe rotor hub 11. Formed onto opposite side-regions of the rotor bladebase 6 are thickening sections 8, 10, which provide an enlargement ofthe cross section of the rotor blade 2 in the direction of the endregion of the rotor blade 2 in the region of the rotor blade base 6.Through the enlarged cross section due to the thickening sections 8, 10formed on both sides of the rotor blades 2, a great degree of strengthis achieved in that area. The thickening sections 8, 10 can be produced,for example, through the application of additional epoxy-resin and fiberlayers.

Provision is made in the region of the rotor blade base 6 for severalrecesses in the form of pocket holes 12, 14, which recesses pass throughthe rotor blade not completely, but only partially; the pocket holeshave a cylindrical form and extend from the surface into the interior ofthe rotor blade 2. The cylindrical pocket holes 12 have a depth thatcorresponds to approximately a third of the entire (cross-sectional)thickness of the rotor blade 2 in the region of the rotor blade base 6.

Arranged inside and laminated into the pocket holes 12, 14 are metalliccross bolts 16, 18 as anchoring elements inside the rotor blade 2. Thecross bolts 16, 18 display in each case a passage bore provided with aninner thread. They work together with tensioning elements 20, 22 in theform of cylindrical bolts made of metal; an outer thread of thetensioning elements 20, 22 is screwed into the inner thread of the crossbolts 16, 18.

The tensioning elements 20, 22 in each case extend through a bore 24, 26arranged inside the rotor blade 2, as well as through a bore 28, 30inside the flange section 4. By means of a nut 32, 34 that can bescrewed onto the outer thread of the tensioning elements 20, 22 and theinterpositioning of a sleeve 36, 38, the tensioning elements 20, 22 canbe acted up with great tensile forces and thus the rotor blade 2 can bedrawn tightly to the flange section 4 and thereby to the rotor hub 11,so that a firm connection between rotor blade 2 and rotor hub 11 isbrought about.

FIG. 3 shows a view of the rotor blade 2 according to a firstimplementation example of the invention represented in FIG. 2, in whichseveral tensioning elements 20, 22 (FIG. 2) are arranged in each case inpairs that are spaced apart from one another in concentric rows. Seen inFIG. 3 are the bores 24, 26 in the rotor blade 2, arranged along twoconcentric, circular rows.

FIG. 4 shows and alternative implementation example of the invention, inwhich the bores 24, 26 and thus also the tensioning elements 20, 22 andthe cross bolts 16, 18 are arranged likewise in two essentiallyconcentric rows along the pipe-shaped rotor blade base 6, the two rowsbeing staggered with respect to each other.

What is claimed is:
 1. Rotor blade for wind energy plant, with at leastone recess, arranged in the region of the rotor blade base and extendingessentially transversely to the longitudinal axis of the rotor blade,for receiving a cross bolt, which is connected to a tensioning elementfor the attachment of the rotor blade to a rotor hub of a wind energyplant, wherein each recess only partially passes through the rotor bladeand is formed as a pocket hole.
 2. Rotor blade according to claim 1,characterized by the fact that the rotor blade displays an enlargedcross section in the region of the rotor blade base and that at leastone pocket hole is arranged in the region of the enlarged cross section.3. Rotor blade according to claim 2, characterized by the fact that thecross section of the rotor blade is enlarged on both sides in thedirection of a hub-side end section of the rotor blade.
 4. Rotor bladeaccording to claim 3, characterized by the fact that the rotor bladedisplays two opposite thickening sections formed as one piece with therotor blade and that the pocket holes are arranged at least partially inthe region of the thickening sections.
 5. Rotor blade according to claim1, characterized by the fact that the rotor blade displays in the regionof the rotor blade base an essentially pipe-shaped end section, in whichare formed on the inside and outside several pocket holes.
 6. Rotorblade according to claim 1, characterized through several boresconnected in each case with a pocket hole and extending essentially inthe direction of the longitudinal axis of the rotor blade, for receivingin each case a tensioning element that is connectable to a cross bolt.7. Rotor blade according to claim 1, characterized by the fact that thepocket hole or holes is/are essentially cylindrical in shape andhas/have a depth that corresponds approximately to a third of the crosssection of the rotor blade in the region of the rotor blade base. 8.Rotor blade according to at least one of the preceding claims,characterized by the fact it consists mainly of a glass-fiber-reinforcedepoxy-resin compound material.
 9. Rotor for a wind energy plant, with arotor hub and at least one rotor blade fastened to the rotor hub,characterized by the fact that at least one rotor blade is formed withat least one recess, arranged in the region of the rotor blade base andextending essentially transversely to the longitudinal axis of the rotorblade, for receiving a cross bolt, which is connected to a tensioningelement for the attachment of the rotor blade to a rotor hub of a windenergy plant, wherein each recess only partially passes through therotor blade and is formed as a pocket hole.
 10. Rotor according to claim9, characterized by the fact that the rotor hub displays a rotary flangesection, essentially T-shaped in cross section, for the connection ofthe rotor blade and that the rotor blade is screwed to the flangesection by means of several tensioning elements, which are connected ineach case to a cross bolt anchored on the rotor blade.
 11. Rotoraccording to claim 10, characterized by the fact that the severaltensioning elements are arranged parallel to each other in pairs and intwo essentially concentrically arranged rows.
 12. Rotor according toclaim 11, characterized by the fact that the tensioning elements of theone row are arranged so as to be displaced in relation to the tensioningelements of the other row.